Diego -- repetitive and maybe somewhat predictable.
BJ Penn -- counters too much. Needs to take the initiative, and make the first move sometimes to change up his game.
Mir -- no wrestling to go to the ground and work his bjj.
Leben -- limited striking defense / non-technical.
Liddell -- should probably be working his wrestling & gnp if his chin is gone.
Rampage -- relies too much on punching power. He either KO's someone or loses on points if he can't connect. He needs a 3rd option.
Bisping & Forrest -- both don't commit to their strikes.

And as a group - British fighters and their wrestling capabilities. We suffer from a huge disadvantage here because we dont learn wrestling at all throughout school/college. And there are very very few wrestling schools to train at in the UK.